People reports that both Affleck and Clinton spoke at the event, which took place at Georgetown University.

During his speech, the actor revealed that when he learned that more than seven million children around the world die before the age of five, he instantly thought of his three children - Violet, 4, Seraphina, 3 and 3-month-old Samuel.

"I have three children who fall into the vulnerable age range," said Affleck, who is married to actress Jennifer Garner. "I cannot imagine what it would've been like driving my wife to the hospital pregnant, about to give birth and thinking to myself, 'Well, there's a 15% chance that each of these children won't live to be five years old'."

Affleck, 39, has been a champion of the issue since 2009, when he founded the Eastern Congo Initiative charity organisation.

He released a special Mother's Day video last month in tribute to the mothers of the Congo.